Field hashCode() method in Java with Examples

Last Updated : 26 Aug, 2019

The hashCode() method of java.lang.reflect.Field used to get the hashcode for this Field. Final Hashcode is computed as the exclusive-or of the hashcodes for the underlying field’s declaring class name and its name. The hashcode is always the same if the object doesn’t change. Hashcode is a unique code generated by the JVM at the time of object creation. It can be used to perform some operation on hashing related algorithm like a hashtable, hashmap etc. An object can also be searched with this unique code.

Syntax:

public int hashCode()

Parameters: This method accepts nothing.

Return value: This method returns an integer which is the hash code value for this object.

Below programs illustrate hashCode() method:
Program 1:

// Java program to demonstrate hashCode() method 
  
import java.lang.reflect.Field; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws Exception 
    { 
  
        // Get the marks field object 
        Field field = User.class.getField("Marks"); 
  
        // Apply hashCode Method on User Object 
        // to get the hashCode of Marks field 
        int value = field.hashCode(); 
  
        // print result 
        System.out.println("HashCode of Marks field"
                           + " is " + value); 
  
        // Now Get the Fees field object 
        field = User.class.getField("Fees"); 
  
        // Apply hashCode Method on User Object 
        // to get the hashcode of Fees field 
        value = field.hashCode(); 
  
        // print result 
        System.out.println("HashCode of Fees field"
                           + " is " + value); 
  
        // Now Get the name field object 
        field = User.class.getField("name"); 
  
        // Apply hashCode Method on User Object 
        // to get the hashCode of name field 
        value = field.hashCode(); 
  
        // print result 
        System.out.println("HashCode of name field"
                           + " is " + value); 
    } 
} 
  
// sample User class 
class User { 
  
    // static double values 
    public static double Marks = 34.13; 
    public static float Fees = 3413.99f; 
    public static String name = "Aman"; 
  
    public static double getMarks() 
    { 
        return Marks; 
    } 
  
    public static void setMarks(double marks) 
    { 
        Marks = marks; 
    } 
  
    public static float getFees() 
    { 
        return Fees; 
    } 
  
    public static void setFees(float fees) 
    { 
        Fees = fees; 
    } 
  
    public static String getName() 
    { 
        return name; 
    } 
  
    public static void setName(String name) 
    { 
        User.name = name; 
    } 
} 

Output:

HashCode of Marks field is 71482573
HashCode of Fees field is 591398
HashCode of name field is 1779040

Program 2:

// Java program to demonstrate hashCode() method 
  
import java.lang.reflect.Field; 
import java.time.Month; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws Exception 
    { 
  
        // Get all field objects of Month class 
        Field[] fields = Month.class.getFields(); 
  
        for (int i = 0; i < fields.length; i++) { 
  
            // print name of Fields 
            System.out.println("HashCode of Field: "
                               + fields[i].hashCode()); 
        } 
    } 
} 

Output:

HashCode of Field: -297508095
HashCode of Field: 1296412905
HashCode of Field: 1475695976
HashCode of Field: 1343692077
HashCode of Field: 1404020238
HashCode of Field: 1401709321
HashCode of Field: 1401709395
HashCode of Field: 538235208
HashCode of Field: 2125827066
HashCode of Field: -1718938229
HashCode of Field: -1007182215
HashCode of Field: 59532142

References: https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Field.html#hashCode–

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